The American Academy of Forensic Science's annual meeting is under way in Seattle, writes James Randerson. It is a truly huge get-together of everyone who is anyone in forensics - nearly 4,000 scientists from all over the world and more than 500 talks and events.

The meeting is themed around "Mass disasters: natural and man made", but there will be plenty else on offer, from drug crime and identity theft to a session titled "Is your daughter trolling for paedophiles on the internet?" and the bizarre-sounding "Tom Krauss memorial bite mark breakfast".

I'll be keeping you posted with regular updates, but first, something much more trivial. Toilet paper. Stay with me on this - there is a point, I promise.

As in many hotels, the final sheet in my current hotel bathroom is folded into a downward pointing V. Now why is that? I mention it because I saw a lecture last week by Dr Susan Blackmore at which she used V-shaped toilet paper as her emblematic example of a "meme".

What is a meme? Well, Dr Blackmore, Queen Bee of the science of "memetics", describes it as "that which is copied" - any idea that is copied from person to person, or person to computer, or phone to computer. The word meme was coined by the Oxford University evolutionist Prof Richard Dawkins when he was drawing parallels between the evolution of ideas and the evolution of genes in his 1976 book The Selfish Gene.

Dr Blackmore was speaking at the British Humanist Association's annual Darwin Day lecture in London. The big guy, who shares his birthday with Abraham Lincoln, was born on February 12 1809.

The "toilet paper V" meme has been copied from hotel to hotel across the world to the point that most of them now do it. Dr Blackmore told her audience that even a remote guesthouse she visited in rural Assam in India did it. And Prof "Darwin's rottweiler" Dawkins chipped in that after using the facilities at the ambassador's residence in Hong Kong he had been practically barged out of the way by a chamber maid anxious to get in to fold the toilet paper.

Why? Could it be to signal that your bathroom has been dealt with in your absence? Or maybe it is meant to give the guest a sort of sadistic pleasure in knowing that some poor eastern European minimum wage-earner has been forced to make this contribution to the bathroom.

One person suggested to me that it was the ultimate symbol of bathroom class because the Queen always insists on it wherever a loo is graced with her presence - any other suggestions gratefully received.

Anyhow, the point here is that the V-shape does not have to be of any use in order to be copied. Memes, like genes, can spread even if they confer no advantage on the person spreading them. Indeed they can spread even if they are detrimental. Think of the genes for a peacock's tail, or the suicide bomber meme.

Back to more serious topics tomorrow, I promise ...

 Science correspondent James Randerson is at the American Academy of Forensic Science conference in Seattle